1. Field of the Invention
The present invention relates generally to methods and apparatus for removing a contaminant from a surface of a liquid, and more particularly to a method utilizing an apparatus including a float in a tubular structure for skimming material from a surface of liquid in a collection reservoir, wherein the apparatus automatically adjusts the float level to accommodate any density or viscosity of liquid.
2. Description of the Prior Art
Many methods and devices for skimming a liquid surface have been conceived to be used in various areas of technology, such as in cleaning the surface water in a swimming pool, and for removing oil from water or other coolants used in machining operations. One of the problems inherent in any such skimming operation is the need to remove only the unwanted surface material liquid, while leaving the desired liquid intact. For example U.S. Pat. No. 5,897,773 by Rhodes describes a funnel-like float device with an open-ended tube attached to the funnel that has its buoyancy carefully calculated to place the lip of the float collection plane at the interface between the upper, lighter liquid to be skimmed off and the lower, heavier liquid. U.S. Pat. No. 5,814,213 by Glasgow describes a similar device having a float with a carefully designed buoyancy to maintain the collection level at an optimum position.
One shortcoming of the prior art devices is that the float can only be designed to effectively accommodate a single set of conditions, those conditions including the thickness and density of the upper liquid and the density of the lower liquid. Therefore, in order to assure complete skimming of the upper fluid in the prior art devices, it is necessary to design the buoyancy of the float so that the collection level is always at or below the interface between the upper and lower fluid. This means that in most cases, a significant quantity of the lower, heavier fluid is skimmed off with the upper fluid. Such an operation is clearly lacking in efficiency. In cases where the lower fluid is, for example, an expensive machine coolant, the inefficiency can be quite costly.
Accordingly, it is an object of the present invention to provide an efficient system of removing a contaminant from a surface of a liquid. The system must be such that only the contaminating fluid is removed, leaving the desired fluid undisturbed.
It is a further object of the present invention to provide a system wherein the float level is self-adjusting so as to accommodate any density or viscosity of liquid.
It is a still further object of the present invention to provide a system that is far less expensive than current art methodology.
It is yet another object of the present invention to provide a system that allows the user to easily and efficiently remove the contaminant fluid from the system.
A preferred embodiment of the present invention includes a liquid surface skimmer having an interior with a wall perimeter sealed by a vertically sliding float. The float has a tubular body with slots in the tube wall, and a vortex cavity in an upper section thereof. The structure of the float provides for flow of liquid from a supply reservoir through the slots in the float wall, over a top edge of the float into the vortex cavity, and then down into the collection reservoir of the float.
The float level is determined by the level of liquid in the collection reservoir. Vertical slots in the wall of the collection reservoir extend above the level of liquid in the supply reservoir. The float body must be sufficiently long so that lower ends of the slots are blocked by the float body. This ensures that liquid from the supply reservoir will flow into the float only at the top edge of the float, thereby enabling the system to effectively separate the desired liquid from the contaminating liquid.
After liquid is accumulated in the collection reservoir of the float, the liquid is pumped at a controlled rate from the collection reservoir to a separation chamber. The liquid in the collection reservoir of the float is initially a mixture of desired liquid and contaminants. The separation chamber allows the liquid to be efficiently removed from the mixture. The contaminating liquid is then removed from the separation chamber for disposal. The remaining liquid is pumped into a filter chamber, where any particulate contamination present in the liquid is removed.
In operation, the surface skimmer is secured in the supply reservoir at a position such that the top of the float body, with the pump off and the system at an at-rest equilibrium, is above the surface level of the liquid in the supply reservoir. The separation process is started by turning the pump on, causing fluid to be pumped from the collection reservoir, which in turn causes the float to drop until the upper edge of the float reaches the level of the liquid in the supply reservoir. At this operating equilibrium point, fluid from the surface of the supply reservoir spills over the float edge, enters the vortex cavity of the float and runs down into the collection reservoir.
If the pump speed is such that the rate of liquid leaving the collection reservoir exceeds the rate of spillage from the supply reservoir into the float, the level of the float continues to drop, and as a result the rate of spillage increases. This continues until the rate of spillage from the supply reservoir into the float equals the rate of evacuation from the collection reservoir to the separation chamber. The initial liquid removed from the supply reservoir will be a mixture of contaminants and desired liquid. As the system operates, the contaminants will be removed until a pure desired liquid remains.